Manual transmission into automatic

Answer 1

It can be done, but it's usually much more rational to replace the car. If it's a RWD you run the risk of having wrong length prop shaft, an unsuitable rear axle gearing, wrong speedo calibration and more. For a FWD I don't quite know. Speedo issue probably still stands, drive shaft lengths may be off, maybe even some of the engine auxillaries may be different. And in these days of integrated electronic engine management there may well an electronig software watchdog or two that gets upset if faced with a new drivetrain configuration.